The present invention relates to a torque transmitting coupling which is ideally suited for use between an engine flywheel and the input shaft for a transmission. More particularly, the invention relates to such a coupling which will isolate the engine firing frequency torque vibrations from the transmission and withstand high torque spikes during start-up, shut down and transmission shifts.
In the operation of an internal-combustion engine, the engine is subjected to an interrupted concentrated force which is brought about by the movement or exciting action of the several pistons and connecting rods operatively connected to the crankshaft. The continuous application of the interrupted force on the crankshaft results in torsional vibrations which are not only felt by the crankshaft, but are transmitted to all components driven by the engine. To isolate the torsional vibrations present in the engine crankshaft it is customary to provide a flywheel on the engine shaft which, by its inertia, evens out the vibrations through energy storage and release. However, the action of the flywheel does not entirely eliminate the transfer of torsional vibration to transmission components downstream from the flywheel and those vibrations which are transmitted have been found to result in transmission performance which is less than would be possible without the presence of such vibrations.
While it is known to provide transmission drive trains with some type of torsional isolator coupling arranged between the flywheels and transmission input shafts for dampening torsional vibrations set up in the crankshafts, often these couplings have one or the other of the faults of not being able to isolate vibrations both under conditions of high and low torque loads and at the same time have the capacity to withstand high torque loading. Contributing to these faults is the fact that heretofore torsional isolator members employed in the couplings have operated at a constant spring rate throughout the entire range of torque loads imposed on the transmission.